A coronavirus vaccine trialed in 108 healthy volunteers in China safely triggered an immune response in the participants, a new study reveals.

Antibody production seen in the patients is a good sign that the vaccine may protect them from infection, but it’s too soon to say for sure.

The Chinese vaccine, made by CanSino, was the very first shot to enter clinical trials earlier this year – months ahead of human testing for the UK’s lead candidate jab – made by Oxford University – or the American lead-contender, made by biotech Moderna.

Most of the people dosed with the vaccine had immune responses, although their levels of antibodies thought to neutralize the virus were relatively low. Researchers saw a stronger ramp-up of other immune compounds, called T-cells, that might also help fight the infection off.

There were side effects – primarily pain, muscle aches and fever – but they subsided within 28 days, and no serious or dangerous side effects were reported.

Promising results from the completed first human trial China’s Ad5 coronavirus vaccine place it at the front of the global race for a shot, though only by a slim margin, an expert told DailyMail.com.

The study, conducted by the collaborating universities and local CDC’s in China, recruited 108 patients ranging in age from 18 to 60, and split them into three groups the received, respectively, low, middle and high doses of the vaccine

At the study’s start, none of the patients – who had never been infected with coronavirus – had neutralizing antibodies against SARS-CoV-2, the virus that causes COVID-19.

Within two weeks, researchers started to see signs that their levels of antibodies were ramping up ‘moderately,’ and peaked 28 days after the volunteers got their shots, according to the study published Friday in The Lancet.

Levels of neutralizing antibodies – a type of immune cell that binds to a virus and may be able to completely block infection – were more than twice as high among the participants who got the high dose shot, compared to those given the low dose.

While any increase in neutralizing antibodies was a significant gain over the subjects’ starting levels (zero), Dr Peter Hotez, a vaccine expert at Baylor College of Medicine in Texas, was unimpressed with the levels produced in the trial participants.

‘The one thing not we’re not seeing is a really high neutralizing antibody titer,’ he told DailyMail.com.

‘The question is whether we’re going to need that and whether these vaccines will be adequate to stimulate an immune response.’

Patients in the trial did have more robust increases in their levels of T cells, immune cells that perform a search and destroy function, rather than the blocking work done by neutralizing antibodies.

More studies will be needed to determine whether the vaccine can protect against infection in practice.

Encouragingly, none of the 108 patients had serious side effects.

More than 80 percent did have some side effects, but these were mostly mild or moderate, like muscle aches, fever, and pain. Most subsided within a couple of weeks, and almost all resolved by the end of the study.

‘That’s pretty good,’ Dr. Hotez says.

Side effect profiles may be particularly important to getting people to get vaccinated against coronavirus once one is available.

A Reuters poll published Thursday found that a quarter of Americans were not very or not at all interested in getting a vaccine for the virus that has infected more than 1.6 million people in the US.

Many of them said they were concerned the vaccine would be riskier than the disease itself because development is moving so fast.

So far, the US government is supporting the development of 14 candidate vaccinations through its Operation Speed initiative.

It’s unclear if the US is coordinating with the Chinese vaccine developers.

In the US and UK, vaccines from Moderna and Oxford University (collaborating with AstaZeneca) are in human trials and have shown promising early results.

China’s completed trial puts it ahead – but not by much, says Dr Hotez. He says that all of the vaccines will need to go through large, Phase III trials before they become available, bringing their timelines to close together.